Ventilation mask with integrated piloted exhalation valve

ABSTRACT

A mask for achieving positive pressure mechanical ventilation (inclusive of CPAP, ventilator support, critical care ventilation, emergency applications), and a method for a operating a ventilation system including such mask. The mask includes a piloted exhalation valve that is used to achieve the target pressures/flows to the patient. The pilot for the valve may be pneumatic and driven from the gas supply tubing from the ventilator. The pilot may also be a preset pressure derived in the mask, a separate pneumatic line from the ventilator, or an electro-mechanical control. The mask of the present invention may further include a heat and moisture exchanger (HME) which is integrated therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. applicationSer. No. 13/411,348 entitled VENTILATION MASK WITH INTEGRATED PILOTEDEXHALATION VALVE filed Mar. 2, 2012, which claims priority to U.S.Provisional Patent Application Ser. No. 61/499,950 entitled VENTILATIONMASK WITH INTEGRATED PILOTED EXHALATION VALVE filed Jun. 22, 2011, andU.S. Provisional Patent Application Ser. No. 61/512,750 entitledVENTILATION MASK WITH INTEGRATED PILOTED EXHALATION VALVE AND METHOD OFVENTILATING A PATIENT USING THE SAME filed Jul. 28, 2011, thedisclosures of which are incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods for controllingdelivery of a pressurized flow of breathable gas to a patient and, moreparticularly, to a ventilation mask such as a full face mask, nasalmask, nasal prongs mask or nasal pillows mask for use in critical careventilation, respiratory insufficiency or OSA (obstructive sleep apnea)with CPAP (Continuous Positive Airway Pressure) therapy andincorporating a piloted exhalation valve inside the mask.

2. Description of the Related Art

As is known in the medical arts, mechanical ventilators comprise medicaldevices that either perform or supplement breathing for patients. Earlyventilators, such as the “iron lung”, created negative pressure aroundthe patient's chest to cause a flow of ambient air through the patient'snose and/or mouth into their lungs. However, the vast majority ofcontemporary ventilators instead use positive pressure to deliver gas tothe patient's lungs via a patient circuit between the ventilator and thepatient. The patient circuit typically consists of one or two large boretubes (e.g., from 22 mm ID for adults to 8 mm ID for pediatric) thatinterface to the ventilator on one end, and a patient mask on the otherend. Most often, the patient mask is not provided as part of theventilator system, and a wide variety of patient masks can be used withany ventilator. The interfaces between the ventilator, patient circuitand patient masks are standardized as generic conical connectors, thesize and shape of which are specified by regulatory bodies (e.g., ISO5356-1 or similar standards).

Current ventilators are designed to support either “vented” or “leak”circuits, or “non-vented” or “non-leak” circuits. In vented circuits,the mask or patient interface is provided with an intentional leak,usually in the form of a plurality of vent openings. Ventilators usingthis configuration are most typically used for less acute clinicalrequirements, such as the treatment of obstructive sleep apnea orrespiratory insufficiency. In non-vented circuits, the patient interfaceis usually not provided with vent openings. Non-vented circuits can havesingle limb or dual limb patient circuits, and an exhalation valve.Ventilators using non-vented patient circuits are most typically usedfor critical care applications.

Vented patient circuits are used only to carry gas flow from theventilator to the patient and patient mask, and require a patient maskwith vent openings. When utilizing vented circuits, the patient inspiresfresh gas from the patient circuit, and expires CO2-enriched gas, whichis purged from the system through the vent openings in the mask. Thisconstant purging of flow through vent openings in the mask when usingsingle-limb circuits provides several disadvantages: 1) it requires theventilator to provide significantly more flow than the patient requires,adding cost/complexity to the ventilator and requiring larger tubing; 2)the constant flow through the vent openings creates and conducts noise,which has proven to be a significant detriment to patients with sleepapnea that are trying to sleep while wearing the mask; 3) the additionalflow coming into proximity of the patient's nose and then exiting thesystem often causes dryness in the patient, which often drives the needfor adding humidification to the system; and 4) patient-expired CO2flows partially out of the vent holes in the mask and partially into thepatient circuit tubing, requiring a minimum flow through the tubing atall times in order to flush the CO2 and minimize the re-breathing ofexhaled CO2. To address the problem of undesirable flow ofpatient-expired CO2 back into the patient circuit tubing, currentlyknown CPAP systems typically have a minimum-required pressure of 4 cmH2O whenever the patient is wearing the mask, which often producessignificant discomfort, claustrophobia and/or feeling of suffocation toearly CPAP users and leads to a high (approximately 50%) non-compliancerate with CPAP therapy.

When utilizing non-vented dual limb circuits, the patient inspires freshgas from one limb (the “inspiratory limb”) of the patient circuit andexpires CO2-enriched gas from the second limb (the “expiratory limb”) ofthe patient circuit. Both limbs of the dual limb patient circuit areconnected together in a “Y” proximal to the patient to allow a singleconical connection to the patient mask. When utilizing non-vented singlelimb circuits, an expiratory valve is placed along the circuit, usuallyproximal to the patient. During the inhalation phase, the exhalationvalve is closed to the ambient and the patient inspires fresh gas fromthe single limb of the patient circuit. During the exhalation phase, thepatient expires CO2-enriched gas from the exhalation valve that is opento ambient. The single limb and exhalation valve are usually connectedto each other and to the patient mask with conical connections.

In the patient circuits described above, the ventilator pressurizes thegas to be delivered to the patient inside the ventilator to the intendedpatient pressure, and then delivers that pressure to the patient throughthe patient circuit. Very small pressure drops develop through thepatient circuit, typically around 1 cm H2O, due to gas flow though thesmall amount of resistance created by the tubing. Some ventilatorscompensate for this small pressure drop either by mathematicalalgorithms, or by sensing the tubing pressure more proximal to thepatient.

Ventilators that utilize a dual limb patient circuit typically includean exhalation valve at the end of the expiratory limb proximal to theventilator, while ventilators that utilize a single limb, non-ventedpatient circuit typically include an exhalation valve at the end of thesingle limb proximal to the patient as indicated above. Exhalationvalves can have fixed or adjustable PEEP (positive expiratory endpressure), typically in single limb configurations, or can be controlledby the ventilator. The ventilator controls the exhalation valve, closesit during inspiration, and opens it during exhalation. Lesssophisticated ventilators have binary control of the exhalation valve,in that they can control it to be either open or closed. Moresophisticated ventilators are able to control the exhalation valve in ananalog fashion, allowing them to control the pressure within the patientcircuit by incrementally opening or closing the valve. Valves thatsupport this incremental control are referred to as active exhalationvalves. In existing ventilation systems, active exhalation valves aremost typically implemented physically within the ventilator, and theremaining few ventilation systems with active exhalation valves locatethe active exhalation valve within the patient circuit proximal to thepatient. Active exhalation valves inside ventilators are typicallyactuated via an electromagnetic coil in the valve, whereas activeexhalation valves in the patient circuit are typically pneumaticallypiloted from the ventilator through a separate pressure source such asecondary blower, or through a proportional valve modulating thepressure delivered by the main pressure source.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a mask(e.g., a nasal pillows mask) for achieving positive pressure mechanicalventilation (inclusive of CPAP, ventilatory support, critical careventilation, emergency applications), and a method for a operating aventilation system including such mask. The mask preferably includes apressure sensing modality proximal to the patient connection. Suchpressure sensing modality may be a pneumatic port with tubing thatallows transmission of the patient pressure back to the ventilator formeasurement, or may include a transducer within the mask. The pressuresensing port is used in the system to allow pressure sensing forachieving and/or monitoring the therapeutic pressures. Alternately oradditionally, the mask may include a flow sensing modality locatedtherewithin for achieving and/or monitoring the therapeutic flows.

The mask of the present invention also includes a piloted exhalationvalve that is used to achieve the target pressures/flows to the patient.In the preferred embodiment, the pilot for the valve is pneumatic anddriven from the gas supply tubing from the ventilator. The pilot canalso be a preset pressure derived in the mask, a separate pneumatic linefrom the ventilator, or an electro-mechanical control. In accordancewith the present invention, the valve is preferably implemented with adiaphragm.

One of the primary benefits attendant to including the valve inside themask is that it provides a path for patient-expired CO2 to exit thesystem without the need for a dual-limb patient circuit, and without thedisadvantages associated with a single-limb patient circuit, such ashigh functional dead space. For instance, in applications treatingpatients with sleep apnea, having the valve inside the mask allowspatients to wear the mask while the treatment pressure is turned offwithout risk of re-breathing excessive CO2.

Another benefit for having the valve inside the mask is that it allowsfor a significant reduction in the required flow generated by theventilator for ventilating the patient since a continuous vented flowfor CO2 washout is not required. Lower flow in turn allows for thetubing size to be significantly smaller (e.g., 2-9 mm ID) compared toconventional ventilators (22 mm ID for adults; 8 mm ID for pediatric).However, this configuration requires higher pressures than the patient'stherapeutic pressure to be delivered by the ventilator. In this regard,pressure from the ventilator is significantly higher than the patient'stherapeutic pressure, though the total pneumatic power delivered isstill smaller than that delivered by a low pressure, high flowventilator used in conjunction with a vented patient circuit andinterface. One obvious benefit of smaller tubing is that it providesless bulk for patient and/or caregivers to manage. For today's smallestventilators, the bulk of the tubing is as significant as the bulk of theventilator. Another benefit of the smaller tubing is that is allows formore convenient ways of affixing the mask to the patient. For instance,the tubing can go around the patient's ears to hold the mask to theface, instead of requiring straps (typically called “headgear”) to affixthe mask to the face. Along these lines, the discomfort, complication,and non-discrete look of the headgear is another significant factorleading to the high non-compliance rate for CPAP therapy. Anotherbenefit to the smaller tubing is that the mask can become smallerbecause it does not need to interface with the large tubing. Indeed,large masks are another significant factor leading to the highnon-compliance rate for CPAP therapy since, in addition to beingnon-discrete, they often cause claustrophobia. Yet another benefit isthat smaller tubing more conveniently routed substantially reduces whatis typically referred to as “tube drag” which is the force that the tubeapplies to the mask, displacing it from the patient's face. This forcehas to be counterbalanced by headgear tension, and the mask movementsmust be mitigated with cushion designs that have great compliance. Thereduction in tube drag in accordance with the present invention allowsfor minimal headgear design (virtually none), reduced headgear tensionfor better patient comfort, and reduced cushion compliance that resultsin a smaller, more discrete cushion.

The mask of the present invention may further include a heat andmoisture exchanger (HME) which is integrated therein. The HME can fullyor at least partially replace a humidifier (cold or heated pass-over;active or passive) which may otherwise be included in the ventilationsystem employing the use of the mask. The HME is positioned within themask so as to be able to intercept the flow delivered from a flowgenerator to the patient in order to humidify it, and further tointercept the exhaled flow of the patient in order to capture humidityand heat for the next breath. The HME can also be used as a structuralmember of the mask, adding a cushioning effect and simplifying thedesign of the cushion thereof.

The present invention is best understood by reference to the followingdetailed description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These, as well as other features of the present invention, will becomemore apparent upon reference to the drawings wherein:

FIG. 1 is top perspective view of a nasal pillows mask constructed inaccordance with one embodiment of the present invention and including anintegrated diaphragm-based piloted exhalation valve;

FIG. 2 is an exploded view of the nasal pillows mask shown in FIG. 1;

FIG. 3 is a partial cross-sectional view of the nasal pillows mask shownin FIG. 1 taken along lines 3-3 thereof, and depicting the valve pilotlumen extending through the cushion of the mask;

FIG. 4 is a partial cross-sectional view of the nasal pillows mask shownin FIG. 1 taken along lines 4-4 thereof, and depicting the pressuresensing lumen extending through the cushion of the mask;

FIG. 5 is a cross-sectional view of the nasal pillows mask shown in FIG.1 taken along lines 5-5 thereof;

FIG. 6 is a top perspective view of cushion of the nasal pillows maskshown in FIG. 1;

FIG. 7 is a top perspective view of exhalation valve of the nasalpillows mask shown in FIG. 1;

FIG. 8 is a bottom perspective view of exhalation valve shown in FIG. 7;

FIG. 9 is a cross-sectional view of exhalation valve shown in FIGS. 7and 8;

FIG. 10 is a cross-sectional view similar to FIG. 5, but depicting avariant of the nasal pillows mask shown in FIG. 1 wherein an HME isintegrated into the cushion thereof;

FIGS. 11A, 11B and 11C are a series of graphs which provide visualrepresentations corresponding to exemplary performance characteristicsof the exhalation valve subassembly of any nasal pillows maskconstructed in accordance with the present invention;

FIG. 12 is a schematic representation of an exemplary ventilation systemwherein a tri-lumen tube is used to facilitate the operative interfacebetween any nasal pillows mask constructed in accordance with thepresent invention a flow generating device;

FIG. 13 is a schematic representation of an exemplary ventilation systemwherein a bi-lumen tube is used to facilitate the operative interfacebetween any nasal pillows mask constructed in accordance with thepresent invention and a flow generating device;

FIG. 14 is a side-elevational view of any nasal pillows mask constructedin accordance with the present invention as cooperatively engagement inan exemplary manner to a patient through the use of a headgear assembly;

FIG. 15 is top perspective view of a nasal pillows mask constructed inaccordance with another embodiment of the present invention andincluding an integrated diaphragm-based piloted exhalation valve;

FIG. 16 is an exploded view of the nasal pillows mask shown in FIG. 15;

FIG. 17 is a partial cross-sectional view of the nasal pillows maskshown in FIG. 15 taken along lines 17-17 thereof, and depicting thevalve pilot lumen extending through the cushion of the mask;

FIG. 18 is a partial cross-sectional view of the nasal pillows maskshown in FIG. 15 taken along lines 18-18 thereof, and depicting thepressure sensing lumen extending through the cushion of the mask;

FIG. 19 is a cross-sectional view of the nasal pillows mask shown inFIG. 15 taken along lines 19-19 thereof;

FIG. 20 is a top perspective view of cushion of the nasal pillows maskshown in FIG. 15;

FIG. 21 is a front elevational view of the exhalation valve subassemblyfor the nasal pillows mask shown in FIG. 15;

FIG. 22 is a front exploded view of the exhalation valve subassemblyshown in FIG. 21, depicting the exhalation valve and the shield platethereof;

FIG. 23 is a rear exploded view of the exhalation valve subassemblyshown in FIG. 21, depicting the exhalation valve and the shield platethereof;

FIG. 24 is a cross-sectional view of the exhalation valve subassemblyshown in FIG. 21 taken along lines 24-24 thereof;

FIG. 25 is a cross-sectional view of the exhalation valve subassemblyshown in FIG. 21 taken along lines 25-25 thereof;

FIG. 26 is a an exploded view of the nasal pillows mask shown in FIG. 15in a partially assembled state prior to the attachment of the framemember to the cushion, and depicting the separation of the strike plateof the exhalation valve subassembly from the exhalation valve thereofwhich is positioned within the cushion;

FIG. 27 is a cross-sectional view similar to FIG. 19, but depicting avariant of the nasal pillows mask shown in FIG. 15 wherein an HME isintegrated into the cushion thereof; and

FIG. 28 is a cross-sectional view similar to FIGS. 17 and 18, butdepicting a variant of the nasal pillows mask shown in FIG. 15 whereinan HME is integrated into the cushion thereof.

Common reference numerals are used throughout the drawings and detaileddescription to indicate like elements.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes ofillustrating various embodiments of the present invention only, and notfor purposes of limiting the same, FIGS. 1-4 depict a ventilation mask10 (e.g., a nasal pillows mask) constructed in accordance with thepresent invention. Though the mask 10 is depicted as a nasal pillowsmask, those skilled in the art will recognize that other ventilationmasks are contemplated herein, such as nasal prongs masks, nasal masks,fill face masks and oronasal masks. As such, for purposes of thisapplication, the term mask and/or ventilation mask is intended toencompass all such mask structures. The mask 10 includes an integrated,diaphragm-implemented, piloted exhalation valve 12, the structural andfunctional attributes of which will be described in more detail below.

As shown in FIGS. 1-5, the mask 10 comprises a housing or cushion 14.The cushion 14, which is preferably fabricated from a silicone elastomerhaving a Shore A hardness in the range of from about 20 to 60 andpreferably about 40, is formed as a single, unitary component, and isshown individually in FIG. 6. The cushion 14 includes a main bodyportion 16 which defines a first outer end surface 18 and an opposedsecond outer end surface 20. The main body portion 16 further defines aninterior fluid chamber 22 which is of a prescribed volume. In additionto the main body portion 16, the cushion 14 includes an identicallyconfigured pair of hollow pillow portions 24 which protrude from themain body portion 16 in a common direction and in a prescribed spatialrelationship relative to each other. More particularly, in the cushion14, the spacing between the pillow portions 24 is selected to facilitatethe general alignment thereof with the nostrils of an adult patient whenthe mask 10 is worn by such patient. As seen in FIGS. 3 and 4, each ofthe pillow portions 24 fluidly communicates with the fluid chamber 22.

As shown in FIG. 2, the main body portion 16 of the cushion 14 includesan enlarged, circularly configured valve opening 26 which is in directfluid communication with the fluid chamber 22. The valve opening 26 ispositioned in generally opposed relation to the pillow portions 24 ofthe cushion 14, and is circumscribed by an annular valve seat 27 alsodefined by the main body portion 16. As also shown in FIG. 2, the mainbody portion 16 further defines opposed first and second inner endsurfaces 28, 30 which protrude outwardly from the periphery of the valveopening 26, and are diametrically opposed relative thereto so as to bespaced by an interval of approximately 180°. The valve opening 26, valveseat 27, and first and second inner end surfaces 28, 30 are adapted toaccommodate the exhalation valve 12 of the mask 10 in a manner whichwill be described in more detail below.

As shown FIGS. 3-6, the main body portion 16 of the cushion 14 furtherdefines first and second gas delivery lumens 32, 34 which extend fromrespective ones of the first and second outer end surfaces 18, 20 intofluid communication with the fluid chamber 22. Additionally, a pressuresensing lumen 36 defined by the main body portion extends from the firstouter end surface 18 into fluid communication with the fluid chamber 22.The main body portion 16 further defines a valve pilot lumen 38 whichextends between the second outer end surface 20 and the second inner endsurface 30. The use of the first and second gas delivery lumens 32, 34,the pressure sensing lumen 36, and the valve pilot lumen 38 will also bediscussed in more detail below. Those of ordinary skill in the art willrecognize that the gas delivery lumens 32, 34, may be substituted with asingle gas delivery lumen and/or positioned within the cushion 14 inorientations other than those depicted in FIG. 6. For example, the gasdelivery lumen(s) of the cushion 14 may be positioned frontally,pointing upwardly, pointing downwardly, etc. rather than extendinglaterally as shown in FIG. 6.

Referring now to FIGS. 2-5 and 7-9, the exhalation valve 12 of the mask10 is made of three (3) parts or components, and more particularly aseat member 40, a cap member 42, and a diaphragm 44 which is operativelycaptured between the seat and cap members 40, 42. The seat and capmembers 40, 42 are each preferably fabricated from a plastic material,with the diaphragm 44 preferably being fabricated from an elastomerhaving a Shore A hardness in the range of from about 20-40.

As is most easily seen in FIGS. 2, 7 and 9, the seat member 40 includesa tubular, generally cylindrical wall portion 46 which defines a distal,annular outer rim 48 and an opposed annular inner seating surface 49. Asshown in FIG. 9, the diameter of the outer rim 48 exceeds that of theseating surface 49. Along these lines, the inner surface of the wallportion 46 is not of a uniform inner diameter, but rather is segregatedinto first and second inner surface sections which are of differinginner diameters, and separated by an annular shoulder 51. In addition tothe wall portion 46, the seat member 40 includes an annular flangeportion 50 which protrudes radially from that end of the wall portion 46opposite the outer rim 48. As shown in FIGS. 2 and 7, the flange portion50 includes a plurality of exhaust vents 52 which are located about theperiphery thereof in a prescribed arrangement and spacing relative toeach other. Additionally, as is apparent from FIG. 9, the seat member 40is formed such that each of the exhaust vents 52 normally fluidlycommunicates with the bore or fluid conduit defined by the wall portion46.

The cap member 42 of the exhaust valve 12 comprises a circularlyconfigured base portion 54 which defines an inner surface 56 and anopposed outer surface 58. In addition to the base portion 54, the capmember 42 includes an annular flange portion 60 which circumvents andprotrudes generally perpendicularly relative to the inner surface 56 ofthe base portion 60. The flange portion 60 defines a distal annularshoulder 62. As shown in FIG. 9, the shoulder 62 and inner surface 56extend along respective ones of a spaced, generally parallel pair ofplanes. Further, as shown in FIG. 8, formed in the outer surface 58 ofthe base portion 54 is an elongate groove 64 which extends diametricallyacross the outer surface 58. The use of the groove 64 will be describedin more detail below. The seat and cap members 40, 42, when attached toeach other in the fully assembled exhalation valve 12, collectivelydefine an interior valve chamber 59 of the exhalation valve 12. Moreparticularly, such valve chamber 59 is generally located between theinner surface 56 defined by the base portion 54 of the cap member 42 andthe seating surface 49 defined by the wall portion 46 of the seat member40.

The diaphragm 44 of the exhalation valve 12, which resides within thevalve chamber 59, has a circularly configured, central body portion 66,and a peripheral flange portion 68 which is integrally connected to andcircumvents the body portion 66. The body portion 66 includes an annularlip 72 which circumvents and protrudes upwardly from one side or facethereof. The flange portion 68 includes an arcuately contoured primaryregion and a distal region which protrudes radially from the primaryregion. As such, the primary region of the flange portion 68 extendsbetween the distal region thereof and the body portion 66, and defines acontinuous, generally concave channel 70.

In the exhalation valve 12, the flange portion 68 of the diaphragm 44 isoperatively captured between the flange portions 50, 60 of the seat andcap members 40, 42. More particularly, the annular distal region of theflange portion 68 is compressed (and thus captured) between the shoulder62 defined by the flange portion 60 of the cap member 42, and acomplimentary annular shoulder 53 which is defined by the flange portion50 of the seat member 40 proximate the exhaust vents 52. The orientationof the diaphragm 44 within the valve chamber 59 when captured betweenthe seat and cap members 40, 42 is such that the channel 70 defined bythe arcuately contoured primary region of the flange portion 68 isdirected toward or faces the seating surface 49 defined by the wallportion 46 of the seat member 40.

The diaphragm 44 (and hence the exhalation valve 12) is selectivelymoveable between an open position (shown in FIGS. 3-5 and 9) and aclosed position. When in its normal, open position, the diaphragm 44 isin a relaxed, unbiased state. Importantly, in either of its open orclosed positions, the diaphragm 44 is not normally seated directlyagainst the inner surface 56 defined by the base portion 54 of the capmember 42. Rather, a gap is normally maintained between the body portion66 of the diaphragm 44 and the inner surface 56 of the base portion 54.The width of such gap when the diaphragm 44 is in its open position isgenerally equal to the fixed distance separating the inner surface 56 ofthe base portion 54 from the shoulder 62 of the flange portion 60.Further, when the diaphragm 44 is in its open position, the body portion66, and in particular the lip 72 protruding therefrom, is itselfdisposed in spaced relation to the seating surface 49 defined by thewall portion 46 of the seat member 40. As such, when the diaphragm 44 isin its open position, fluid is able to freely pass through the fluidconduit defined by the wall portion 46, between the seating surface 49and diaphragm 44, and through the exhaust vents 52 to ambient air. Asshown in FIGS. 3, 8 and 9, the flange portion 60 of the cap member 42 isfurther provided with a pilot port 74 which extends therethrough and, inthe fully assembled exhalation valve 12, fluidly communicates with thatportion of the valve chamber 59 disposed between the body portion 66 ofthe diaphragm 44 and the inner surface 56 of the base portion 54. Theuse of the pilot port 74 will also be described in more detail below.

As will be discussed in more detail below, in the exhalation valve 12,the diaphragm 44 is resiliently deformable from its open position (towhich it may be normally biased) to its closed position. An importantfeature of the present invention is that the diaphragm 44 is normallybiased to its open position which provides a failsafe to allow a patientto inhale ambient air through the exhalation valve 12 and exhale ambientair therethrough (via the exhaust vents 52) during any ventilatormalfunction or when the mask 10 is worn without the therapy beingdelivered by the ventilator. When the diaphragm 44 is moved or actuatedto its closed position, the lip 72 of the body portion 66 is firmlyseated against the seating surface 49 defined by the wall portion 46 ofthe seat member 40. The seating of the lip 72 against the seatingsurface 49 effectively blocks fluid communication between the fluidconduit defined by the wall portion 46 and the valve chamber 59 (andhence the exhaust vents 52 which fluidly communicate with the valvechamber 59).

In the mask 10, the cooperative engagement between the exhalation valve12 and the cushion 14 is facilitated by the advancement of the wallportion 46 of the seat member 40 into the valve opening 26 defined bythe cushion 14. As best seen in FIG. 5, such advancement is limited bythe ultimate abutment or engagement of a beveled seating surface 76defined by the flange portion 50 of the seat member 40 against thecomplimentary valve seat 27 of the cushion 14 circumventing the valveopening 26. Upon the engagement of the seating surface 76 to the valveseat 27, the fluid chamber 22 of the cushion 14 fluidly communicateswith the fluid conduit defined by the wall portion 46 of the seat member40. As will be recognized, if the diaphragm 44 resides in its normal,open position, the fluid chamber 22 is further placed into fluidcommunication with the valve chamber 59 via the fluid conduit defined bythe wall portion 46, neither end of which is blocked or obstructed byvirtue of the gap defined between the lip 72 of the diaphragm 44 and theseating surface 49 of the wall portion 46.

When the exhalation valve 12 is operatively coupled to the cushion 14,in addition to the valve seat 27 being seated against the seatingsurface 76, the first and second inner end surfaces 28, 30 of thecushion 14 are seated against respective, diametrically opposed sectionsof the flange portion 68 defined by the cap member 42. As best seen inFIGS. 3 and 4, the orientation of the exhalation valve 12 relative tothe cushion 14 is such that the end of the valve pilot lumen 38extending to the second inner end surface 30 is aligned and fluidlycommunicates with the pilot port 74 within the flange portion 60. Assuch, in the mask 10, the valve pilot lumen 38 is in continuous, fluidcommunication with that portion of the valve chamber 59 defined betweenthe inner surface 56 of the base portion 54 and the body portion 66 ofthe diaphragm 44.

To assist in maintaining the cooperative engagement between theexhalation valve 12 and the cushion 14, the mask 10 is furtherpreferably provided with an elongate frame member 78. The frame member78 has a generally V-shaped configuration, with a central portionthereof being accommodated by and secured within the complimentarygroove 64 formed in the outer surface 58 defined by the base portion 54of the cap member 42. As shown in FIGS. 3 and 4, the opposed endportions of the frame members 78 are cooperatively engaged to respectiveones of the first and second outer end surfaces 18, 20 of the cushion14. More particularly, as shown in FIG. 2, the frame member 78 includesan identically configured pair of first and second connectors 80, 82which extend from respective ones of the opposed end portions thereof.An inner portion of the first connector 80 is advanced into andfrictionally retained within the first gas delivery lumen 32 of thecushion 14. Similarly, an inner portion of the second connector 82 isadvanced into and frictionally retained within the second gas deliverylumen 34 of the cushion 14. In addition to the inner portions advancedinto respective ones of the first and second gas delivery lumens 32, 34,the first and second connectors 80, 82 of the frame member 78 eachfurther include an outer portion which, as will be described in moredetail below, is adapted to be advanced into and frictionally retainedwithin a corresponding lumen of a respective one of a pair of bi-lumentubes fluidly coupled to the mask 10.

As shown in FIGS. 3 and 4, the frame member 78 further includes atubular, cylindrically configured pressure port 84 which is disposedadjacent the first connector 80. The pressure port 84 is aligned andfluidly communicates with the pressure sensing lumen 36 of the cushion14. Similarly, the frame member 78 is also provided with a tubular,cylindrically configured pilot port 86 which is disposed adjacent thesecond connector 82. The pilot port 86 is aligned and fluidlycommunicates with the valve pilot lumen 38 of the cushion 14. As willalso be discussed in more detail below, the pressure and pilot ports 84,86 of the frame member 78 are adapted to be advanced into andfrictionally maintained within corresponding lumens of respective onesof the aforementioned pair of bi-lumen tubes which are fluidly connectedto the mask 10 within a ventilation system incorporating the same. Thereceipt of the frame member 78 within the groove 64 of the cap member 42ensures that the cushion 14, the exhalation valve 12 and the framemember 78 are properly aligned, and prevents relative movementtherebetween. Though not shown, it is contemplated that in one potentialvariation of the mask 10, the cushion 14 may be formed so as not toinclude the valve pilot lumen 38. Rather, a suitable valve pilot lumenwould be formed directly within the frame member 78 so as to extendtherein between the pilot port 86 thereof and the pilot port 74 of theexhalation valve 12.

In the mask 10, the exhalation valve 12 is piloted, with the movement ofthe diaphragm 44 to the closed position described above beingfacilitated by the introduction of positive fluid pressure into thevalve chamber 59. More particularly, it is contemplated that during theinspiratory phase of the breathing cycle of a patient wearing the mask10, the valve pilot lumen 38 will be pressurized by a pilot line fluidlycoupled to the pilot port 86, with pilot pressure being introduced intothat portion of the valve chamber 59 normally defined between the bodyportion 66 of the diaphragm 44 and the inner surface 56 defined by thebase portion 54 of the cap member 42 via the pilot port 74 extendingthrough the flange portion 60 of the cap member 42. The fluid pressurelevel introduced into the aforementioned region of the valve chamber 59via the pilot port 74 will be sufficient to facilitate the movement ofthe diaphragm 44 to its closed position described above.

Conversely, during the expiratory phase of the breathing cycle of thepatient wearing the mask 10, it is contemplated that the discontinuationor modulation of the fluid pressure through the valve pilot lumen 38 andhence into the aforementioned region of the valve chamber 59 via thepilot port 74, coupled with the resiliency of the diaphragm 44 and/orpositive pressure applied to the body portion 66 thereof, willfacilitate the movement of the diaphragm 44 back to the open position orto a partially open position. In this regard, positive pressure as maybe used to facilitate the movement of the diaphragm 44 to its openposition may be provided by air which is exhaled from the patient duringthe expiratory phase of the breathing circuit and is applied to the bodyportion 66 via the pillows portions 24 of the cushion 14, the fluidchamber 22, and the fluid conduit defined by the wall portion of theseat member 40. As will be recognized, the movement of the diaphragm 44to the open position allows the air exhaled from the patient to bevented to ambient air after entering the valve chamber 59 via theexhaust vents 52 within the flange portion 50 of the seat member 40which, as indicated above, fluidly communicate with the valve chamber59.

As will be recognized, based on the application of pilot pressurethereto, the diaphragm 44 travels from a fully open position through apartially open position to a fully closed position. In this regard, thediaphragm 44 will be partially open or partially closed duringexhalation to maintain desired ventilation therapy. Further, when pilotpressure is discontinued to the diaphragm 44, it moves to an openposition wherein the patient can inhale and exhale through the mask 10with minimal restriction and with minimal carbon dioxide retentiontherein. This is an important feature of the present invention whichallows a patient to wear the mask 10 without ventilation therapy beingapplied to the mask 10, the aforementioned structural and functionalfeatures of the mask 10 making it more comfortable to wear, and furtherallowing it to be worn without carbon dioxide buildup. This feature ishighly advantageous for the treatment of obstructive sleep apnea whereinpatients complain of discomfort with ventilation therapy due to mask andpressure discomfort. When it is detected that a patient requires sleepapnea therapy, the ventilation therapy can be started (i.e., in anobstructive sleep apnea situation).

To succinctly summarize the foregoing description of the structural andfunctional features of the mask 10, during patient inhalation, the valvepilot lumen 38 is pressurized, which causes the diaphragm 44 to closeagainst the seating surface 49, thus effectively isolating the fluidchamber 22 of the mask 10 from the outside ambient air. The entire flowdelivered from a flow generator fluidly coupled to the mask 10 isinhaled by the patient, assuming that unintentional leaks at theinterface between the cushion 14 and the patient are discarded. Thisfunctionality differs from what typically occurs in a conventional CPAPmask, where venting to ambient air is constantly open, and anintentional leak flow is continuously expelled to ambient air. Duringpatient exhalation, the pilot pressure introduced into the valve pilotlumen 38 is controlled so that the exhaled flow from the patient can beexhausted to ambient air through the exhalation valve 12 in theaforementioned manner. In this regard, the pilot pressure is “servoed”so that the position of the diaphragm 44 relative to the seating surface49 is modulated, hence modulating the resistance of the exhalation valve12 to the exhaled flow and effectively ensuring that the pressure in thefluid chamber 22 of the mask 10 is maintained at a prescribedtherapeutic level throughout the entire length of the exhalation phase.When the valve pilot lumen 38 is not pressurized, the exhalation valve12 is in a normally open state, with the diaphragm 44 being spaced fromthe seating surface 49 in the aforementioned manner, thus allowing thepatient to spontaneously breathe in and out with minimal pressure drop(also referred to as back-pressure) in the order of less than about 2 cmH2O at 60 l/min. As a result, the patient can comfortably breathe whilewearing the mask 10 and while therapy is not being administered to thepatient.

Referring now to FIGS. 11A, 11B and 11C, during use of the mask 10 by apatient, the functionality of the exhalation valve 12 can becharacterized with three parameters. These are Pt which is the treatmentpressure (i.e., the pressure in the mask 10 used to treat the patient;Pp which is the pilot pressure (i.e., the pressure used to pilot thediaphragm 44 in the exhalation valve 12); and Qv which is vented flow(i.e., flow that is exhausted from inside the exhalation valve 12 toambient. These three particular parameters are labeled as Pt, Pp and Qvin FIG. 9. When the patient is ventilated, Pt is greater than zero, withthe functionality of the exhalation valve 12 being described by thefamily of curves in the first and second quadrants of FIG. 11A. In thisregard, as apparent from FIG. 11A, for any given Pt, it is evident thatby increasing the pilot pressure Pp, the exhalation valve 12 will closeand the vented flow will decrease. A decrease in the pilot pressure Ppwill facilitate the opening of the valve 12, thereby increasing ventedflow. The vented flow will increase until the diaphragm 44 touches orcontacts the inner surface 56 of the base portion 54 of the cap member42, and is thus not able to open further. Conversely, when the patientis not ventilated, the inspiratory phase can be described by the thirdand fourth quadrants. More particularly, Qv is negative and air entersthe mask 10 through the valve 12, with the pressure Pt in the mask 10being less than or equal to zero. Pilot pressure Pp less than zero isnot a configuration normally used during ventilation of the patient, butis depicted for a complete description of the functionality of the valve12. The family of curves shown in FIG. 11A can be described by aparametric equation. Further, the slope and asymptotes of the curvesshown in FIG. 11A can be modified by, for example and not by way oflimitation, changing the material used to fabricate the diaphragm 44,changing the thickness of the diaphragm 44, changing the area ratiobetween the pilot side and patient side of the diaphragm 44, changingthe clearance between the diaphragm 44 and the seating surface 49,and/or changing the geometry of the exhaust vents 52.

An alternative representation of the functional characteristics of thevalve 12 can be described by graphs in which ΔP=Pt−Pp is shown. Forexample, the graph of FIG. 11B shows that for any given Pt, the ventedflow can be modulated by changing ΔP. In this regard, ΔP can beinterpreted as the physical position of the diaphragm 44. Since thediaphragm 44 acts like a spring, the equation describing the relativeposition d of the diaphragm 44 from the seating surface 49 of the seatmember 40 is k·d+Pt·At =Pp·Ap, where At is the area of the diaphragm 44exposed to treatment pressure Pt and Ap is the area of the diaphragm 44exposed to the pilot pressure Pp. A similar, alternative representationis provided in the graph of FIG. 11C which shows Pt on the x-axis and ΔPas the parameter. In this regard, for any given ΔP, the position d ofthe diaphragm 44 is determined, with the valve 12 thus being consideredas a fixed opening valve. In this scenario Pt can be considered thedriving pressure pushing air out of the valve 12, with FIG. 11C furtherillustrating the highly non-linear behavior of the valve 12.

FIG. 12 provides a schematic representation of an exemplary ventilationsystem 88 wherein a tri-lumen tube 90 is used to facilitate the fluidcommunication between the mask 10 and a blower or flow generator 92 ofthe system 88. As represented in FIG. 12, one end of the tri-lumen tube90 is fluidly connected to the flow generator 92, with the opposite endthereof being fluidly connected to a Y-connector 94. The three lumensdefined by the tri-lumen tube 90 include a gas delivery lumen, apressure sensing lumen, and a valve pilot lumen. The gas delivery lumenis provided with an inner diameter or ID in the range of from about 2 mmto 15 mm, and preferably about 4 mm to 10 mm. The pressure sensing andvalve pilot lumens of the tri-lumen tube 90 are each preferably providedwith an ID in the range of from about 0.5 mm to 2 mm. The outer diameteror OD of the tri-lumen tube 90 is preferably less than 17 mm, with thelength thereof in the system 88 being about 2 m. The Y-connector 94effectively bifurcates the tri-lumen tube 90 into the first and secondbi-lumen tubes 96, 98, each of which has a length of about 6 inches. Thefirst bi-lumen tube 96 includes a gas delivery lumen having an ID in thesame ranges described above in relation to the gas delivery lumen of thetri-lumen tube 90. The gas delivery lumen of the first bi-lumen tube 96is fluidly coupled to the outer portion of the first connector 80 of theframe member 78. The remaining lumen of the first bi-lumen tube 96 is apressure sensing lumen which has an ID in the same range described abovein relation to the pressure sensing lumen of the tri-lumen tube 90, andis fluidly coupled to the pressure port 84 of the frame member 78.Similarly, the second bi-lumen tube 98 includes a gas delivery lumenhaving an ID in the same ranges described above in relation to the gasdelivery lumen of the tri-lumen tube 90. The gas delivery lumen of thesecond bi-lumen tube 98 is fluidly coupled to the outer portion of thesecond connector 82 of the frame member 78. The remaining lumen of thesecond bi-lumen tube 98 is a valve pilot lumen which has an ID in thesame range described above in relation to the valve pilot lumen of thetri-lumen tube 90, and is fluidly coupled to the pilot port 86 of theframe member 78.

In the system 88 shown in FIG. 12, the pilot pressure is generated atthe flow generator 92. In the prior art, a secondary blower orproportional valve that modulates the pressure from a main blower isused to generate a pressure to drive an expiratory valve. However, inthe system 88 shown in FIG. 12, the outlet pressure of the flowgenerator 92 is used, with the flow generator 92 further beingcontrolled during patient exhalation in order to have the correct pilotpressure for the exhalation valve 12. This allows the system 88 to beinexpensive, not needing additional expensive components such asproportional valves or secondary blowers.

FIG. 13 provides a schematic representation of another exemplaryventilation system 100 wherein a bi-lumen tube 102 is used to facilitatethe fluid communication between the mask 10 and the blower or flowgenerator 92 of the system 100. As represented in FIG. 13, one end ofthe bi-lumen tube 102 is fluidly connected to the flow generator 92,with the opposite end thereof being fluidly connected to the Y-connector94. The two lumens defined by the bi-lumen tube 102 include a gasdelivery lumen and a pressure sensing lumen. The gas delivery lumen isprovided with an inner diameter or ID in the range of from about 2 mm to10 mm, and preferably about 4 mm to 7 mm. The pressure sensing lumen ofthe bi-lumen tube 102 is preferably provided with an ID in the range offrom about 0.5 mm to 2 mm. The outer diameter or OD of the bi-lumen tube90 is preferably less than 11 mm, with the length thereof being about 2m. The Y-connector 94 effectively bifurcates the bi-lumen tube 102 intothe first and second bi-lumen tubes 96, 98, each of which has a lengthof about 6 inches. The first bi-lumen tube 96 includes a gas deliverylumen having an ID in the same ranges described above in relation to thegas delivery lumen of the bi-lumen tube 102. The gas delivery lumen ofthe first bi-lumen tube 96 is fluidly coupled to the outer portion ofthe first connector 80 of the frame member 78. The remaining lumen ofthe first bi-lumen tube 96 is a pressure sensing lumen which has an IDin the same range described above in relation to the pressure sensinglumen of the bi-lumen tube 102, and is fluidly coupled to the pressureport 84 of the frame member 78. Similarly, the second bi-lumen tube 98includes a gas delivery lumen having an ID in the same ranges describedabove in relation to the gas delivery lumen of the bi-lumen tube 102.The gas delivery lumen of the second bi-lumen tube 98 is fluidly coupledto the outer portion of the second connector 82 of the frame member 78.The remaining lumen of the second bi-lumen tube 98 is a valve pilotlumen which has an ID in the same range described above in relation tothe pressure sensing lumen of the bi-lumen tube 102, and is fluidlycoupled to the pilot port 86 of the frame member 78.

In the system 100 shown in FIG. 13, the valve pilot lumen 38 isconnected to the gas delivery air path at the Y-connector 94. Moreparticularly, the gas delivery lumen of the bi-lumen tube 102 istransitioned at the Y-connector 94 to the valve pilot lumen of thesecond bi-lumen tube 98. As such, the pilot pressure will beproportional to the outlet pressure of the flow generator 92 minus thepressure drop along the bi-lumen tube 102, which is proportional todelivered flow. This solution is useful when small diameter tubes areused in the system 100, since such small diameter tubes require higheroutlet pressure from the flow generator 92 for the same flow. In thisregard, since the pressure at the outlet of the flow generator 92 wouldbe excessive for piloting the exhalation valve 12, a lower pressurealong the circuit within the system 100 is used. In the system 100,though it is easier to tap in at the Y-connector 94, anywhere along thetube network is acceptable, depending on the pressure level of the flowgenerator 92 which is the pressure required by the patient circuit inorder to deliver the therapeutic pressure and flow at the patient.

In each of the systems 88, 100, it is contemplated that the control ofthe flow generator 92, and hence the control of therapeutic pressuredelivered to the patient wearing the mask 10, may be governed by thedata gathered from dual pressure sensors which take measurements at themask 10 and the output of the flow generator 92. As will be recognized,pressure sensing at the mask 10 is facilitated by the pressure sensinglumen 36 which, as indicated above, is formed within the cushion 14 andfluidly communicates with the fluid chamber 22 thereof. As alsopreviously explained, one of the lumens of the first bi-lumen tube 96 ineach of the systems 88, 100 is coupled to the pressure port 84 (andhence the pressure sensing lumen 36). As a result, the first bi-lumentube 96, Y-connector 94 and one of the tri-lumen or bi-lumen tubes 90,102 collectively define a continuous pressure sensing fluid path betweenthe mask 10 and a suitable pressure sensing modality located remotelytherefrom. A more detailed discussion regarding the use of the dualpressure sensors to govern the delivery of therapeutic pressure to thepatient is found in Applicant's co-pending U.S. application Ser. No.13/411,257 entitled Dual Pressure Sensor Continuous Positive AirwayPressure (CPAP) Therapy filed Mar. 2, 2012, the entire disclosure ofwhich is incorporated herein by reference.

Referring now to FIG. 10, there is shown a mask 10 a which comprises avariant of the mask 10. The sole distinction between the masks 10, 10 alies in the mask 10 a including a heat and moisture exchanger or HME 104which is positioned within the fluid chamber 22 of the cushion 14. TheHME 104 is operative to partially or completely replace a humidifier(cold or heated pass-over; active or passive) which would otherwise befluidly coupled to the mask 10 a. This is possible because the averageflow through the system envisioned to be used in conjunction with themask 10 a is about half of a prior art CPAP mask, due to the absence ofany intentional leak in such system.

The HME 104 as a result of its positioning within the fluid chamber 22,is able to intercept the flow delivered from the flow generator to thepatient in order to humidify it, and is further able to capture humidityand heat from exhaled flow for the next breath. The pressure dropcreated by the HME 104 during exhalation (back-pressure) must belimited, in the order of less than 5 cm H2O at 60 l/min, and preferablylower than 2 cm H2O at 60 l/min. These parameters allow for a lowback-pressure when the patient is wearing the mask 10 a and no therapyis delivered to the patient.

It is contemplated that the HME 104 can be permanently assembled to thecushion 14, or may alternatively be removable therefrom and thuswashable and/or disposable. In this regard, the HME 104, if removablefrom within the cushion 14, could be replaced on a prescribedreplacement cycle. Additionally, it is contemplated that the HME 104 canbe used as an elastic member that adds elasticity to the cushion 14. Inthis regard, part of the elasticity of the cushion 14 may beattributable to its silicone construction, and further be partlyattributable to the compression and deflection of the HME 104 inside thecushion 14.

Referring now to FIGS. 15-19, there is shown a ventilation mask 110(e.g., a nasal pillows mask) constructed in accordance with anotherembodiment of the present invention. Like the mask 10 described above,the mask 110 includes an integrated, diaphragm-implemented, pilotedexhalation valve 112, the structural and functional attributes of whichwill be described in more detail below.

As shown in FIGS. 15-19, the mask 110 comprises a housing or cushion114. The cushion 114, which is preferably fabricated from a siliconeelastomer having a Shore A hardness in the range of from about 20 to 60and preferably about 40, is formed as a single, unitary component, andis shown individually in FIG. 20. The cushion 114 includes a main bodyportion 116 which defines a first outer end surface 118 and an opposedsecond outer end surface 120. The main body portion 116 further definesan interior fluid chamber 122 which is of a prescribed volume. Inaddition to the main body portion 116, the cushion 14 includes anidentically configured pair of hollow pillow portions 124 which protrudefrom the main body portion 116 in a common direction and in a prescribedspatial relationship relative to each other. More particularly, in thecushion 114, the spacing between the pillow portions 124 is selected tofacilitate the general alignment thereof with the nostrils of an adultpatient when the mask 110 is worn by such patient. Each of the pillowportions 124 fluidly communicates with the fluid chamber 122.

As shown in FIG. 16, the main body portion 116 of the cushion 114includes an enlarged, circularly configured valve opening 126 which isin direct fluid communication with the fluid chamber 122. The valveopening 126 is positioned in generally opposed relation to the pillowportions 124 of the cushion 114. The valve opening 126 is adapted toaccommodate an exhalation valve subassembly 111 of the mask 110 in amanner which will be described in more detail below.

The main body portion 116 of the cushion 114 further defines first andsecond gas delivery lumens 132, 134 which extend from respective ones ofthe first and second outer end surfaces 118, 120 into fluidcommunication with the fluid chamber 122. Additionally, a pressuresensing lumen 136 defined by the main body portion 116 extends from thefirst outer end surface 118 into fluid communication with the fluidchamber 122. The main body portion 116 further defines a valve pilotlumen 138 which extends from the second outer end surface 120 into fluidcommunication with the fluid chamber. Those of ordinary skill in the artwill recognize that the gas delivery lumens 132, 134 may be substitutedwith a single gas delivery lumen and/or positioned within the cushion114 in orientations other than those depicted in FIG. 20. For example,the gas delivery lumen(s) of the cushion 114 may be positionedfrontally, pointing upwardly, pointing downwardly, etc. rather thanextending laterally as shown in FIG. 20. The main body portion 116 ofthe cushion 114 further includes a mounting aperture 139 formed therein.As seen in FIG. 18, one end of the mounting aperture 139 communicateswith the fluid chamber 122, with the opposite simply terminating blindlywithin the main body portion 116. The use of the first and second gasdelivery lumens 132, 134, the pressure sensing lumen 136, the valvepilot lumen 138 and the mounting aperture 139 will be discussed in moredetail below.

Referring now to FIGS. 16-19 and 21-26, the exhalation valve subassembly111 of the mask 110 comprises the aforementioned exhalation valve 112 incombination with a shield plate 113. The exhalation valve 112 of themask 110 is itself made of three (3) parts or components, and moreparticularly a seat member 140, a cap member 142, and a diaphragm 144which is operatively captured between the seat and cap members 140, 142.The seat and cap members 140, 142 are each preferably fabricated from aplastic material, with the diaphragm 144 preferably being fabricatedfrom an elastomer having a Shore A hardness in the range of from about20-40.

The seat member 140 includes a tubular, generally cylindrical wallportion 146 which defines a distal, annular outer rim 148 and an opposedannular inner seating surface 149. The wall portion further defines anoutlet conduit 147 which extends between the outer rim 148 and seatingsurface 149. In addition to the wall portion 146, the seat member 140includes an annular flange portion 150 which is integrally connected tothe wall portion 146 by a series of spoke portions 151. The spokeportions 151 extend to locations on the wall portion 146 proximate theseating surface 149, with the flange portion 150 being positionedradially outward relative to the wall portion 146. In the seat member140, the wall, flange and spoke portions 146, 150, 151 collectivelydefine a plurality of exhaust vents 152 which are located about theperiphery of the wall portion 146 in a prescribed arrangement andspacing relative to each other. The seat member 140 is formed such thateach of the exhaust vents 152 normally fluidly communicates with theoutlet conduit 147 defined by the wall portion 146.

The cap member 142 of the exhalation valve 112 comprises a circularlyconfigured base portion 154 which defines an inner surface 156. Inaddition to the base portion 154, the cap member 142 includes an annularflange portion 160 which circumvents and protrudes generallyperpendicularly relative to the inner surface 156 of the base portion154. The cap member 142 further includes an identically configured pairof tube portions 162 which are integrally connected to the flangeportion 160 in diametrically opposed relation to each other (i.e.,approximately 180° apart). Each of the tube portions defines a lumen 164extending therethrough and is used for reasons which will be discussedin more detail below. The seat and cap members 140, 142, when attachedto each other in the fully assembled exhalation valve 112, collectivelydefine an interior valve chamber of the exhalation valve 112, such valvechamber generally being located between the inner surface 156 defined bythe base portion 154 of the cap member 142 and the seating surface 149defined by the wall portion 146 of the seat member 140.

The diaphragm 144 of the exhalation valve 112, which resides within thevalve chamber, has a circularly configured, central body portion 166,and a peripheral flange portion 168 which is integrally connected to andcircumvents the body portion 166. The flange portion 168 includes anarcuately contoured primary region and a distal region which protrudesradially from the primary region. As such, the primary region of theflange portion 168 extends between the distal region thereof and thebody portion 166, and defines a continuous, generally concave channel170. The body portion 166 of the diaphragm 144 may optionally beperforated, i.e., be provided with an array of small apertures whichextend therethrough.

In the exhalation valve 112, the flange portion 168 of the diaphragm 144is operatively captured between complementary engagement surfacesdefined by the flange portions 150, 160 of the seat and cap members 140,142. More particularly, the annular distal region of the flange portion168 is compressed (and thus captured) between an annular shoulderdefined by the flange portion 160 of the cap member 142, and acomplimentary annular shoulder which is defined by the flange portion150 of the seat member 140 proximate the exhaust vents 152. Theorientation of the diaphragm 144 within the valve chamber when capturedbetween the seat and cap members 140, 142 is such that the channel 170defined by the arcuately contoured primary region of the flange portion168 is directed toward or faces the seating surface 149 defined by thewall portion 146 of the seat member 140.

The capture of the diaphragm 144 between the seat and cap members 140,142 in the aforementioned manner results in the diaphragm 144effectively segregating the valve chamber collectively defined by theseat and cap members 140, 142 into a pilot section 172 and an exhaustsection 174. The pilot section 172 of the valve chamber is locatedbetween the diaphragm 144 and the inner surface 156 of the base portion154 of the cap member 142. The exhaust section 174 of the valve chamberis located between the diaphragm 144 and both the exhaust vents 152 andthe seating surface 149 of the wall portion 146 of the seat member 140.In this regard, the outlet conduit 147 defined by the wall portion 146fluidly communicates with the exhaust section 174 of the valve chamber.In addition, the lumens 164 of the tube portions 162 of the cap member142 each fluidly communicate with the pilot section 172 of the valvechamber.

The diaphragm 144 (and hence the exhalation valve 112) is selectivelymoveable between an open position (shown in FIGS. 17-19 and 24-25) and aclosed position. When in its normal, open position, the diaphragm 144 isin a relaxed, unbiased state. Importantly, in either of its open orclosed positions, the diaphragm 144 is not normally seated directlyagainst the inner surface 156 defined by the base portion 154 of the capmember 142. Rather, a gap is normally maintained between the bodyportion 166 of the diaphragm 144 and the inner surface 156 of the baseportion 154. The width of such gap when the diaphragm 144 is in its openposition is generally equal to the fixed distance separating the innersurface 156 of the base portion 154 from the shoulder of the flangeportion 160 which engages the distal region of the flange portion 168 ofthe diaphragm 144. Further, when the diaphragm 144 is in its openposition, the body portion 166 is itself disposed in spaced relation tothe seating surface 149 defined by the wall portion 146 of the seatmember 140. As such, when the diaphragm 144 is in its open position,fluid is able to freely pass through the through the exhaust vents 152,between the seating surface 149 and diaphragm 144, and through theoutlet conduit 147 defined by the wall portion 146 to ambient air.

In the exhalation valve 112, the diaphragm 144 is resiliently deformablefrom its open position (to which it may be normally biased) to itsclosed position. An important feature of the present invention is thatthe diaphragm 144 is normally biased to its open position which providesa failsafe to allow a patient to inhale ambient air through theexhalation valve 112 and exhale ambient air therethrough (via theexhaust vents 52) during any ventilator malfunction or when the mask 110is worn without the therapy being delivered by the ventilator. When thediaphragm 144 is moved or actuated to its closed position, the peripheryof the body portion 166 is firmly seated against the seating surface 149defined by the wall portion 146 of the seat member 140. The seating ofthe body portion 166 of the diaphragm 144 against the seating surface149 effectively blocks fluid communication between the outlet conduit147 defined by the wall portion 146 and the exhaust section 174 of thevalve chamber (and hence the exhaust vents 152 which fluidly communicatewith the exhaust section 174).

In the mask 110, the cooperative engagement between the exhalation valve112 and the cushion 114 is facilitated by the advancement of the capmember 142 into the valve opening 126 defined by the cushion 114.Subsequent to such advancement, one of the two tube portions 162 of thecap member 142 is partially advanced into and frictionally retainedwithin the pilot lumen 138 of the cushion 114 in the manner shown inFIG. 17. As is apparent from FIG. 17, the advancement of one tubeportion 162 of the cap member 142 into the pilot lumen 138 facilitatesthe placement of the pilot lumen 138 into fluid communication with thepilot section 172 of the valve chamber via the lumen 164 of thecorresponding tube portion 162. The remaining tube portion 162 of thecap member 142 (i.e., that tube portion 162 not advanced into the pilotlumen 138) is advanced into and frictionally retained within theabove-described mounting aperture 139 in the manner shown in FIG. 18.Importantly, the resilient construction of the cushion 114, and inparticular the main body 116 thereof, allows for the cushion 114 to bebent, twisted or otherwise manipulated as is needed to facilitate theadvancement of the tube portions 162 of the cap member 142 intorespective ones of the pilot lumen 138 and mounting aperture 139 in theaforementioned manner. The advancement of the tube portions 162 intorespective ones of the pilot lumen 138 and mounting aperture 139 causesthe exhalation valve 112 to assume a position within the fluid chamber122 of the cushion 114 as is best shown in FIG. 26. In this regard, themajority of the exhalation valve 112 resides within the fluid chamber122, with the exception of a small distal section of the wall portion148 of the seat member 140 which protrudes from the valve opening 126 ofthe cushion 114.

Due to the positioning of the majority of the exhalation valve 114within the fluid chamber 122, the exhaust section 174 of the valvechamber is placed into direct fluid communication with the fluid chamber122 via the exhaust vents 152. Thus, irrespective of whether thediaphragm 144 of the exhalation valve 112 is in its open or closedpositions, the pilot lumen 138 of the cushion 114 is maintained in aconstant state of fluid communication with the pilot section 172 of thevalve chamber. Additionally, irrespective of whether the diaphragm 144is in its open or closed positions, the fluid chamber 122 is maintainedin a constant state of fluid communication with the exhaust section 174of the valve chamber via the exhaust vents 152. When the diaphragm 144is in its open position, the fluid chamber 122 is further placed intofluid communication with both the outlet conduit 147 (and hence ambientair) via the open flow path defined between the body portion 166 of thediaphragm 144 and the seating surface 149 of the wall portion 146 of theseat member 140. However, when the diaphragm 144 is moved to its closedposition, the fluid communication between the fluid chamber 122 andoutlet conduit 147 is effectively blocked by the sealed engagement ofthe body portion 166 of the diaphragm 144 against the seating surface149 of the wall portion 146.

As indicated above, in addition to the exhalation valve 112, theexhalation valve subassembly 111 includes the shield plate 113. Theshield plate 113 has a generally oval, slightly arcuate profile, andincludes a circularly configured opening 175 within the approximatecenter thereof. Additionally, formed within the peripheral side surfaceof the shield plate 113 is an elongate groove or channel 176. In themask 110, the shield plate 113 is adapted to be advanced into the valveopening 126 subsequent to the cooperative engagement of the exhalationvalve 112 to the cushion 114 in the aforementioned manner. Moreparticularly, the advancement of the shield plate 113 into the valveopening 126 is facilitated in a manner wherein the wall portion 146 ofthe seat member 140 is advanced into and through the opening 175 of theshield plate 113. In this regard, the wall portion 146 and the opening175 have complimentary configurations, with the diameter of the opening175 only slightly exceeding that of the outer diameter of the wallportion 148.

Subsequent to the advancement of the wall portion 148 into the opening175, that peripheral edge or lip of the main body 116 of the cushion 114defining the valve opening 126 is advanced into and firmly seated withinthe complimentary channel 176 formed in the peripheral side surface ofthe shield plate 113. The receipt of such edge or lip of the cushion 114into the channel 176 maintains the shield plate 113 in firm, frictionalengagement to the cushion 114. As is seen in FIGS. 17 and 18, thespatial relationship between the exhalation valve 112 and shield plate113 when each is cooperatively engaged to the cushion 114 in theaforementioned manner is such that the distal section of the wallportion 146 which defines the outer rim 148 thereof protrudes slightlyfrom the exterior surface of the shield plate 113.

As will be recognized, the shield plate 113, when cooperatively engagedto the cushion 114, effectively encloses that portion of the fluidchamber 122 which would otherwise be directly accessible via the valveopening 126. Importantly, by virtue of the attachment of the shieldplate 113 to the main body 116 of the cushion 114, virtually theentirety of the exhalation valve 112 is completely enclosed or containedwithin the fluid chamber 122 of the cushion 114. As indicated above,only a small distal section of the wall portion 146 of the seat member140 protrudes from the shield plate 113, and in particular the opening175 defined thereby. As a result, the exhaust vents 152 which facilitatethe fluid communication between the fluid chamber 122 and the exhaustsection 174 of the valve chamber, and between the fluid chamber 122 andthe outlet conduit 147 (and hence ambient air) when the diaphragm 144 isin the open position, are effectively enclosed within the fluid chamber122 as provides noise attenuation advantages which will be discussed inmore detail below.

To assist in maintaining the cooperative engagement between theexhalation valve subassembly 111 and the cushion 114, the mask 110 isfurther preferably provided with an elongate reinforcement frame member178 which is attached to the cushion 114. The frame member 178 has agenerally U-shaped configuration, with a central portion thereofincluding a circularly configured opening 179 formed therein which isadapted to accommodate that aforementioned distal section of the wallportion 146 of the seat member 140 which protrudes from the shield plate113. In this regard, the diameter of the opening 179 is sized so as toonly slightly exceed the outer diameter of the wall portion 146. As seenin FIG. 15, the thickness of the central portion of the frame member 178is such that when attached to cushion 114 subsequent to the advancementof the wall portion 146 into the complementary opening 179, the outerrim 148 defined by the wall portion 146 is substantially flush orcontinuous with the exterior surface of the frame member 178.

As shown in FIGS. 17 and 18, the opposed end portions of the framemember 178 are cooperatively engaged to respective ones of the first andsecond outer end surfaces 118, 120 of the cushion 114. Moreparticularly, the frame member 178 includes an identically configuredpair of first and second connectors 180, 182 which are formed onrespective ones of the opposed end portions thereof. An inner portion ofthe first connector 180 is advanced into and frictionally retainedwithin the first gas delivery lumen 132 of the cushion 114. Similarly,an inner portion of the second connector 182 is advanced into andfrictionally retained within the second gas delivery lumen 134 of thecushion 114. In addition to the inner portions advanced into respectiveones of the first and second gas delivery lumens 132, 134, the first andsecond connectors 180, 182 of the frame member 178 each further includean outer portion which is adapted to be advanced into and frictionallyretained within a corresponding lumen of a respective one of a pair ofbi-lumen tubes fluidly coupled to the mask 110, in the same manner asdescribed in detail above in relation to the mask 10.

The frame member 178 further includes a tubular, cylindricallyconfigured pressure port 184 which is disposed adjacent the firstconnector 180. The pressure port 184 is aligned and fluidly communicateswith the pressure sensing lumen 136 of the cushion 114. Similarly, theframe member 178 is also provided with a tubular, cylindricallyconfigured pilot port 186 which is disposed adjacent the secondconnector 182. The pilot port 186 is aligned and fluidly communicateswith the valve pilot lumen 138 of the cushion 114. The pressure andpilot ports 184, 186 of the frame member 78 are adapted to be placedinto fluid communication with corresponding lumens of respective ones ofthe aforementioned pair of bi-lumen tubes which are fluidly connected tothe mask 110 within a ventilation system incorporating the same, also inthe same manner as described in detail above in relation to the mask 10.The receipt of the wall portion 146 of the seat member 140 into theopening 179 of the frame member 178 ensures that the cushion 114, theexhalation valve subassembly 111 and the frame member 178 are properlyaligned, and prevents relative movement therebetween.

In the mask 110, the exhalation valve 112 is piloted, with the movementof the diaphragm 144 to the closed position described above beingfacilitated by the introduction of positive fluid pressure into thepilot section 172 of the valve chamber. More particularly, it iscontemplated that during the inspiratory phase of the breathing cycle ofa patient wearing the mask 110, the valve pilot lumen 138 will bepressurized by a pilot line fluidly coupled to the pilot port 186, withpilot pressure being introduced into that portion of the pilot section172 of the valve chamber via the pilot lumen 138 and the lumen 164 ofthat tube portion 162 of the cap member 142 advanced into the pilotlumen 138. The fluid pressure level introduced into the pilot section172 of the valve chamber will be sufficient to facilitate the movementof the diaphragm 144 to its closed position described above. When thediaphragm 144 is in its closed position, fluid pressure introduced intothe fluid chamber 122 via the gas delivery lumens 136, 138 is preventedfrom being exhausted to ambient air. In this regard, though such fluidmay flow from the fluid chamber 122 into the exhaust section 174 of thevalve chamber via the exhaust vents 152, the engagement of the diaphragm144 to the seating surface 149 defined by the wall portion 146 of theseat member 140 effectively blocks the flow of such fluid into theoutlet conduit defined by the wall portion 146 and hence to ambient air.

Conversely, during the expiratory phase of the breathing cycle of thepatient wearing the mask 110, it is contemplated that thediscontinuation or modulation of the fluid pressure through the valvepilot lumen 138 and hence into the pilot section 172 of the valvechamber, coupled with the resiliency of the diaphragm 144 and/orpositive pressure applied to the body portion 166 thereof, willfacilitate the movement of the diaphragm 144 back to the open positionor to a partially open position. In this regard, positive pressure asmay be used to facilitate the movement of the diaphragm 144 to its openposition may be provided by air which is exhaled from the patient duringthe expiratory phase of the breathing circuit and is applied to the bodyportion 166 of the diaphragm 144 via the pillows portions 124 of thecushion 114, the fluid chamber 122, the exhaust vents 152, and theexhaust section 174 of the valve chamber. As will be recognized, themovement of the diaphragm 144 to the open position allows the airexhaled from the patient into the fluid chamber 122 via the pillowportions 124 to be vented to ambient air after flowing from the fluidchamber 122 into the exhaust section 174 of the valve chamber via theexhaust vents 152, and thereafter flowing from the exhaust section 174between the diaphragm 144 and seating surface 149 of the wall portion146 into the outlet conduit 147 also defined by the wall portion 146.

As will be recognized, based on the application of pilot pressurethereto, the diaphragm 144 travels from a fully open position through apartially open position to a fully closed position. In this regard, thediaphragm 144 will be partially open or partially closed duringexhalation to maintain desired ventilation therapy. Further, when pilotpressure is discontinued to the diaphragm 144, it moves to an openposition wherein the patient can inhale and exhale through the mask 110with minimal restriction and with minimal carbon dioxide retentiontherein. This is an important feature of the present invention whichallows a patient to wear the mask 110 without ventilation therapy beingapplied to the mask 110, the aforementioned structural and functionalfeatures of the mask 110 making it more comfortable to wear, and furtherallowing it to be worn without carbon dioxide buildup. This feature ishighly advantageous for the treatment of obstructive sleep apnea whereinpatients complain of discomfort with ventilation therapy due to mask andpressure discomfort. When it is detected that a patient requires sleepapnea therapy, the ventilation therapy can be started (i.e., in anobstructive sleep apnea situation).

To succinctly summarize the foregoing description of the structural andfunctional features of the mask 110, during patient inhalation, thevalve pilot lumen 138 is pressurized, which causes the diaphragm 144 toclose against the seating surface 149, thus effectively isolating thefluid chamber 122 of the mask 110 from the outside ambient air. Theentire flow delivered from a flow generator fluidly coupled to the mask110 is inhaled by the patient, assuming that unintentional leaks at theinterface between the cushion 114 and the patient are discarded. Thisfunctionality differs from what typically occurs in a conventional CPAPmask, where venting to ambient air is constantly open, and anintentional leak flow is continuously expelled to ambient air. Duringpatient exhalation, the pilot pressure introduced into the valve pilotlumen 138 is controlled so that the exhaled flow from the patient can beexhausted to ambient air through the exhalation valve 112 in theaforementioned manner. In this regard, the pilot pressure is “servoed”so that the position of the diaphragm 144 relative to the seatingsurface 149 is modulated, hence modulating the resistance of theexhalation valve 112 to the exhaled flow and effectively ensuring thatthe pressure in the fluid chamber 122 of the mask 110 is maintained at aprescribed therapeutic level throughout the entire length of theexhalation phase. When the valve pilot lumen 138 is not pressurized, theexhalation valve 112 is in a normally open state, with the diaphragm 144being spaced from the seating surface 149 in the aforementioned manner,thus allowing the patient to spontaneously breathe in and out withminimal pressure drop (also referred to as back-pressure) in the orderof less than about 2 cm H2O at 60 l/min. As a result, the patient cancomfortably breathe while wearing the mask 110 and while therapy is notbeing administered to the patient. Importantly, the effectivecontainment of the exhaust vents 152 within the fluid chamber 122substantially mitigates or suppresses the noise generated by the mask110 attributable to the flow of fluid into the exhaust section 174 ofthe valve chamber via the exhaust vents 152.

Those of ordinary skill in the art will recognize that the functionalityof the exhalation valve 112 during use of the mask 110 by a patient canbe characterized with the same three parameters described above inrelation to the mask 10 and shown in FIGS. 11A, 11B and 11C. However,based on the structural features of the exhalation valve 112 incomparison to the exhalation valve 12, the parameters Pt which is thetreatment pressure (i.e., the pressure in the mask 110 used to treat thepatient; Pp which is the pilot pressure (i.e., the pressure used topilot the diaphragm 144 in the exhalation valve 112); and Qv which isvented flow (i.e., flow that is exhausted from inside the exhalationvalve 112 to ambient are labeled in FIG. 18 as Pt, Pp and Qv in thecontext of the exhalation valve 112. As such, when the patient isventilated, Pt is greater than zero, with the functionality of theexhalation valve 112 being described by the family of curves in thefirst and second quadrants of FIG. 11A. In this regard, as apparent fromFIG. 11A, for any given Pt, it is evident that by increasing the pilotpressure Pp, the exhalation valve 112 will close and the vented flowwill decrease. A decrease in the pilot pressure Pp will facilitate theopening of the exhalation valve 112, thereby increasing vented flow. Thevented flow will increase until the diaphragm 144 touches or contactsthe inner surface 156 of the base portion 154 of the cap member 142, andis thus not able to open further. Conversely, when the patient is notventilated, the inspiratory phase can be described by the third andfourth quadrants. More particularly, Qv is negative and air enters themask 110 through the exhalation valve 112, with the pressure Pt in themask 110 being less than or equal to zero. Pilot pressure Pp less thanzero is not a configuration normally used during ventilation of thepatient, but is depicted for a complete description of the functionalityof the exhalation valve 112. The family of curves shown in FIG. 11A canbe described by a parametric equation. Further, the slope and asymptotesof the curves shown in FIG. 11A can be modified by, for example and notby way of limitation, changing the material used to fabricate thediaphragm 144, changing the thickness of the diaphragm 144, changing thearea ratio between the side of the diaphragm 144 facing the pilotsection 172 and the side facing the exhaust section 174, changing theclearance between the diaphragm 144 and the seating surface 149, and/orchanging the geometry of the exhaust vents 152.

As also discussed above in relation to the mask 10, an alternativerepresentation of the functional characteristics of the valve 112 can bedescribed by graphs in which ΔP=Pt−Pp is shown. For example, the graphof FIG. 11B shows that for any given Pt, the vented flow can bemodulated by changing ΔP. In this regard, ΔP can be interpreted as thephysical position of the diaphragm 144. Since the diaphragm 144 actslike a spring, the equation describing the relative position d of thediaphragm 144 from the seating surface 149 of the seat member 140 isk·d+Pt·At=Pp·Ap, where At is the area of the diaphragm 144 exposed totreatment pressure Pt and Ap is the area of the diaphragm 144 exposed tothe pilot pressure Pp. A similar, alternative representation is providedin the graph of FIG. 11C which shows Pt on the x-axis and ΔP as theparameter. In this regard, for any given ΔP, the position d of thediaphragm 144 is determined, with the exhalation valve 112 thus beingconsidered as a fixed opening valve. In this scenario Pt can beconsidered the driving pressure pushing air out of the exhalation valve112, with FIG. 11C further illustrating the highly non-linear behaviorof the valve 112.

The mask 110 may also be integrated into each of the above-describedventilation systems 88, 100 in substitution for the mask 10. In thisregard, as will be recognized by those of ordinary skill in the art, thefirst and second bi-lumen tubes 96, 98 of such ventilation systems 88,100 would simply be cooperatively engaged to corresponding ones of thefirst and second connectors 180, 182, pressure port 184 and pilot port186 of the frame member 178 in the same manner described above regardingthe engagement to the first and second connectors 80, 82, pressure port84 and pilot port 86 of the frame member 78.

In the mask 110, it is contemplated that exhalation vale subassembly111, and in particular the exhalation valve 112, may be detached fromthe cushion 114 and removed from within the fluid chamber 122 as neededfor periodic cleaning or replacement thereof. As will be recognized,such removal is facilitated by first detaching the shield plate 113 fromthe cushion 114 by removing the lip of the cushion 114 defining thevalve opening 126 from within the channel 176 of the shield plate 113.Thereafter, the exhalation valve 112 is simply grasped and pulled fromwithin the fluid chamber 122, the flexibility/resiliency of the cushion114 allowing for the easy removal of the tube portions 162 of the capmember 142 from within respective ones of the pilot lumen 138 andmounting aperture 139. The re-attachment of the exhalation valvesubassembly 111 to the cushion 114 occurs in the reverse sequence, theexhalation valve 112 being advanced into the fluid chamber 122 andattached to the cushion 114 in the aforementioned manner prior to theattachment of the shield plate 113 to the cushion 114 in theaforementioned manner.

Referring now to FIGS. 27 and 28, there is shown a mask 110 a whichcomprises a variant of the mask 110. The sole distinction between themasks 110, 110 a lies in the mask 110 a including a heat and moistureexchanger or HME 204 which is positioned within the fluid chamber 122 ofthe cushion 114. The HME 204 is operative to partially or completelyreplace a humidifier (cold or heated pass-over; active or passive) whichwould otherwise be fluidly coupled to the mask 110 a. This is possiblebecause the average flow through the system envisioned to be used inconjunction with the mask 110 a is about half of a prior art CPAP mask,due to the absence of any intentional leak in such system.

The HME 204, as a result of its positioning within the fluid chamber122, is able to interact with the flow delivered from the flow generatorto the patient in order to humidify it, and is further able to capturehumidity and heat from exhaled flow for the next breath. The pressuredrop created by the HME 204 during exhalation (back-pressure) must belimited, in the order of less than 5 cm H2O at 60 l/min, and preferablylower than 2 cm H2O at 60 l/min. These parameters allow for a lowback-pressure when the patient is wearing the mask 110 a and no therapyis delivered to the patient.

It is contemplated that the HME 204 can be permanently assembled to thecushion 114, or may alternatively be removable therefrom and thuswashable and/or disposable. In this regard, the HME 204, if removablefrom within the cushion 114, could be replaced on a prescribedreplacement cycle. As will be recognized, the removal of the HME 204from within the fluid chamber 122 would follow the detachment of theexhalation valve subassembly 111 from the cushion 114 in the mannerdescribed above. Similarly, the placement of the HME 204 back into thefluid chamber 122 would precede the reattachment of the exhalation valvesubassembly 111 to the cushion 114 in the manner also described above.Additionally, it is contemplated that the HME 204 can be used as anelastic member that adds elasticity to the cushion 114. In this regard,part of the elasticity of the cushion 114 may be attributable to itssilicone construction, and further be partly attributable to thecompression and deflection of the HME 204 inside the cushion 114.

The integration of the exhalation valve 12, 112 into the cushion 14, 114and in accordance with the present invention allows lower average flowcompared to prior art CPAP masks. As indicated above, normal masks havea set of apertures called “vents” that create a continuous intentionalleak during therapy. This intentional leak or vented flow is used toflush out the exhaled carbon dioxide that in conventional CPAP machines,with a standard ISO taper tube connecting the mask to the flow generatoror blower, fills the tubing up almost completely with carbon dioxideduring exhalation. The carbon dioxide accumulated in the tubing, if notflushed out through the vent flow, would be inhaled by the patient inthe next breath, progressively increasing the carbon dioxide content inthe inhaled gas at every breath. The structural/functional features ofthe exhalation valve 12, 112, in conjunction with the use of small innerdiameter, high pneumatic resistance tubes in the system in which themask 10, 10 a, 110, 110 a is used, ensures that all the exhaled gas goesto ambient. As a result, a vent flow is not needed for flushing anytrapped carbon dioxide out of the system. Further, during inspirationthe exhalation valve 12, 112 can close, and the flow generator of thesystem needs to deliver only the patient flow, without the additionaloverhead of the intentional leak flow. In turn, the need for lower flowrates allows for the use of smaller tubes that have higher pneumaticresistance, without the need for the use of extremely powerful flowgenerators. The pneumatic power through the system can be keptcomparable to those of traditional CPAP machines, though the pressuredelivered by the flow generator will be higher and the flow lower.

The reduced average flow through the system in which the mask 10, 10 a,110, 110 a is used means that less humidity will be removed from thesystem, as well as the patient. Conventional CPAP systems have toreintegrate the humidity vented by the intentional leak using ahumidifier, with heated humidifiers being the industry standard. Activehumidification introduces additional problems such as rain-out in thesystem tubing, which in turn requires heated tubes, and thus introducingmore complexity and cost into the system. The envisioned system of thepresent invention, as not having any intentional leak flow, does notneed to introduce additional humidity into the system. As indicatedabove, the HME 104, 204 can be introduced into the cushion 14, 114 ofthe mask 10 a, 110 a so that exhaled humidity can be trapped and used tohumidify the air for the following breath.

In addition, a big portion of the noise of conventional CPAP systems isnoise conducted from the flow generator through the tubing up to themask and then radiated in the ambient through the vent openings. Aspreviously explained, the system described above is closed to theambient during inhalation which is the noisiest part of the therapy. Theexhaled flow is also lower than the prior art so it can be diffused moreefficiently, thus effectively decreasing the average exit speed andminimizing impingement noise of the exhaled flow on bed sheets, pillows,etc.

As also explained above, a patient can breathe spontaneously when themask 10, 10 a, 110, 100 a is worn and not connected to the flowgenerator tubing, or when therapy is not administered. In this regard,there will be little back pressure and virtually no carbon dioxidere-breathing, due to the presence of the exhalation valve 12, 112 thatis normally open and the inner diameters of the tubes integrated intothe system. This enables a zero pressure start wherein the patient fallsasleep wearing the mask 10, 10 a, 110, 110 a wherein the flow generatordoes not deliver any therapy. Prior art systems can only ramp from about4 m H2O up to therapy pressure. A zero pressure start is morecomfortable to patients that do not tolerate pressure.

As seen in FIG. 14, due to the reduced diameter of the various tubes(i.e., the tri-lumen tube 90 and bi-lumen tubes 96, 98, 102) integratedinto the system 88, 100, such tubes can be routed around the patient'sears similar to conventional O2 cannulas. More particularly, the tubingcan go around the patient's ears to hold the mask 10, 10 a, 110, 110 ato the patient's face. This removes the “tube drag” problem describedabove since the tubes will not pull the mask 10, 10 a away from the faceof the patient when he or she moves. As previously explained, “tubedrag” typically decreases mask stability on the patient and increasesunintentional leak that annoys the patient. In the prior art, head geartension is used to counter balance the tube drag, which leads to comfortissues. The tube routing of the present invention allows for lower headgear tension and a more comfortable therapy, especially for compliantpatients that wear the mask 10, 10 a, 110, 110 a approximately eighthours every night. The reduction in tube drag in accordance with thepresent invention also allows for minimal headgear design (virtuallynone), reduced headgear tension for better patient comfort as indicatedabove, and reduced cushion compliance that results in a smaller, morediscrete cushion 14, 114. The tube dangling in front of the patient,also commonly referred to as the “elephant trunk” by patients, is asubstantial psychological barrier to getting used to therapy. The tuberouting shown in FIG. 14, in addition to making the mask 10, 10 a, 110,110 a more stable upon the patient, avoids this barrier as well. Anotherbenefit to the smaller tubing is that the mask 10, 10 a, 110, 110 a canbecome smaller because it does not need to interface with large tubing.Indeed, large masks are another significant factor leading to the highnon-compliance rate for CPAP therapy since, in addition to beingnon-discrete, they often cause claustrophobia.

This disclosure provides exemplary embodiments of the present invention.The scope of the present invention is not limited by these exemplaryembodiments. Numerous variations, whether explicitly provided for by thespecification or implied by the specification, such as variations instructure, dimension, type of material and manufacturing process may beimplemented by one of skill in the art in view of this disclosure.

What is claimed is:
 1. A ventilation mask, comprising: a housing sizedand configured to be positionable between a patient's nose and mouth incontact with the patient's nose, the housing defining an internal fluidchamber, at least one gas delivery lumen which fluidly communicates withthe fluid chamber, and a valve pilot lumen; and a piloted exhalationvalve attached to the housing and at least partially residing within thefluid chamber thereof, the exhalation valve comprising: a valve housingdefining a valve chamber which fluidly communicates with the fluidchamber, the pilot lumen and ambient air; and a diaphragm disposedwithin the valve chamber, the diaphragm normally being biased to an openposition wherein the fluid chamber fluidly communicates with ambient airvia the valve chamber, and a closed position wherein fluid communicationbetween the fluid chamber and ambient air is blocked thereby, themovement of the diaphragm from the open position to the closed positionbeing facilitated by the selective pressurization of at least a portionof the valve chamber via the pilot lumen.
 2. The ventilation mask ofclaim 1 wherein the housing further defines a pressure sensing lumenwhich fluidly communicates with the fluid chamber.
 3. The ventilationmask of claim 1 wherein the housing is a resilient cushion including aspaced pair of hollow pillow portions which each fluidly communicatewith the fluid chamber and are adapted to engage respective ones of thenostrils of the patient's nose.
 4. The ventilation mask of claim 3further comprising a heat and moisture exchanger disposed within thefluid chamber between the exhalation valve and the pillow portions ofthe cushion.
 5. The ventilation mask of claim 3 wherein the valvehousing comprises: a seat member; and a cap member attached to the seatmember, the seat and cap members collectively defining the valvechamber; the diaphragm being captured between the seat and cap membersin a manner wherein the diaphragm effectively segregates the valvechamber into a pilot section which fluidly communicates with the pilotlumen and an exhaust section which fluidly communicates with the fluidchamber in ambient air.
 6. The ventilation mask of claim 5 wherein thediaphragm and the seat member define complimentary seating surfaceswhich are sized and configured relative to each other such that themovement of the diaphragm to the closed position facilitates theplacement of the seating surfaces into sealed engagement with each otherin a manner blocking fluid communication between the fluid chamber andambient air.
 7. The ventilation mask of claim 6 wherein the seat memberincludes a plurality of vents which are disposed therein andcollectively define a fluid conduit between the fluid chamber and theexhaust section of the valve chamber.
 8. The ventilation mask of claim 7wherein the vents of the seat member reside within the fluid chamber ofthe cushion.
 9. The ventilation mask of claim 8 further comprising ashield plate attached to the cushion and partially defining the fluidchamber, the shield plate including an opening therein which is sizedand configured to accommodate a portion of the seat member.
 10. Theventilation mask of claim 9 further comprising a reinforcement framemember which is attached to the cushion, the frame member spanning theshield plate and including an opening therein which is coaxially alignedwith the opening of the shield plate and is size and configured toaccommodate a portion of the seat member.
 11. A ventilation mask,comprising: a housing sized and configured to be positionable between apatient's nose and mouth in contact with the patient's nose, the housingdefining an internal fluid chamber; and an exhalation valve attached tothe housing and at least partially residing within the fluid chamberthereof, the exhalation valve comprising: a valve housing defining avalve chamber which fluidly communicates with the fluid chamber via atleast one vent and with ambient air via at least one outlet conduit; anda diaphragm disposed within the valve chamber, the diaphragm beingselectively movable between an open position wherein the fluid chamberfluidly communicates with ambient air via the valve chamber, and aclosed position wherein fluid communication between the fluid chamberand ambient air is blocked thereby; the vent of the valve housingresiding and being enclosed within the fluid chamber, with the outletconduit of the valve housing protruding from the fluid chamber.
 12. Theventilation mask of claim 11 wherein the housing is a resilient cushionincluding a spaced pair of hollow pillow portions which each fluidlycommunicate with the fluid chamber and are adapted to engage respectiveones of the nostrils of a patient's nose.
 13. The ventilation mask ofclaim 12 further comprising a heat and moisture exchanger disposedwithin the fluid chamber between the exhalation valve and the pillowportions of the cushion.
 14. The ventilation mask of claim 12 whereinthe valve housing comprises: a seat member defining the vent and theoutlet conduit; and a cap member attached to the seat member, the seatand cap members collectively defining the valve chamber; the diaphragmbeing captured between the seat and cap members in a manner wherein thediaphragm effectively segregates the valve chamber into at least twosections, one of which fluidly communicates with the vent and the outletconduit.
 15. The ventilation mask of claim 14 wherein the diaphragm andthe seat member define complimentary seating surfaces and are sized andconfigured relative to each other such that the movement of thediaphragm to the closed position facilitates the placement of theseating surfaces into sealed engagement with each other in a mannerblocking fluid communication between the vent and the outlet conduit.16. The ventilation mask of claim 15 wherein the seat member includes aplurality of vents which collectively define a fluid conduit.
 17. Theventilation mask of claim 15 further comprising a shield plate attachedto the cushion and partially defining the fluid chamber, the shieldplate including an opening therein which is sized and configured toaccommodate a portion of the seat member which defines the outletconduit thereof.
 18. The ventilation mask of claim 17 further comprisinga reinforcement frame member which is attached to the cushion, the framemember spanning the shield plate and including an opening therein whichis coaxially aligned with the opening of the shield plate and is sizedand configured to accommodate the portion of the seat member whichdefines the outlet conduit thereof.
 19. A ventilation mask, comprising:a housing sized and configured to be positionable between a patient'snose and mouth in contact with the patient's nose, the housing definingan internal fluid chamber, at least one gas delivery lumen which fluidlycommunicates with the fluid chamber, and a valve pilot lumen; and anexhalation valve at least partially residing within the fluid chamber ofthe housing, the exhalation valve including: a valve chamber whichfluidly communicates with the fluid chamber, the pilot lumen and ambientair; and a diaphragm which is disposed within the valve chamber, thediaphragm being movable between an open position wherein the fluidchamber fluidly communicates with ambient air via the valve chamber, anda closed position wherein fluid communication between the fluid chamberand ambient air is blocked thereby; the movement of the diaphragm fromthe open position to the closed position being facilitated by theselective pressurization of at least a portion of the valve chamber viathe pilot lumen.
 20. The ventilation mask of claim 19 wherein thehousing further defines a pressure sensing lumen which fluidlycommunicates with the fluid chamber.